docs: def comma_replacement(random, population, parents, offspring, args):
      """Performs "comma" replacement.
      
      This function performs "comma" replacement, which means that
      the entire existing population is replaced by the best
      population-many elements from the offspring. This function
      makes the assumption that the size of the offspring is at 
      least as large as the original population. Otherwise, the
      population size will not be constant.
      
      .. Arguments:
         random -- the random number generator object
         population -- the population of individuals
         parents -- the list of parent individuals
         offspring -- the list of offspring individuals
         args -- a dictionary of keyword arguments
         
      """
      offspring.sort(reverse=True)
      survivors = offspring[:len(population)]
      return survivors